The page below is a sample from the LabCE course Histology Special Stains: Carbohydrates. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

Gluteraldehyde should be avoided as a tissue fixative since it is a dialdehyde that will react with this reagent and give false-positive PAS staining.

4

Potassium metabisulfite:

0.55% solution

1 minute in 2 changes

While some technicians omit this reagent step in the protocol with no problems, metabisulfite rinses may be necessary to remove any excess leucofuchsin left over after exposure to the Schiff reagent. Highly chlorinated water can cause these excess molecules to nonspecifically stain other tissue elements in the section.

5

Running tap water

Up to 10 minutes

Warm to hot running water develops the PAS stain and gives a more intense staining reaction than cold water.